Bass and Treble Dials

It seems every high end audiophile quality preamp/amp comes with no bass/treble dials. There is no way to adjust the sound coming out of the system other than by adding, removing or replace the audio equipment components... such as the needles, tubes, cables and etc etc. I wonder what would be a real reason behind of not having the treble/bass dials? While it might be a simple question but I really don't know the exact answer. I only guess that it is because the adding the treble/bass dials will unavoidably make an electronic circuit more "complex" which would go against a whole concept: "the simpler the better" or "the less is more". Am I correct in my assumptions?